1. Field of Invention
The present invention relates to switch power supply, more particularly, relates to a green (environmentally friendly) switch power supply with standby function, the switch power supply comprises a standby power source, a main power source having a remote control, a PFC (power factor correction) device, and an supplementary circuit, wherein a monolithic green on/off power supply integrated circuit or thick film circuit, or modular circuit are applied, and the main power is controlled by a remote signal in response to an error signal, and finally, the present invention also provides a PC standard (ATX, ATX12, and SSI) for the power supply.
2. Description of Related Arts
Switching power converters are used in a wide variety of applications to convert electrical power from one form to another form. For example, DC/DC converters are used to convert DC power provided at one voltage level to DC power at another voltage level and AC-DC converters are employed to convert alternate current power into direct current power. At the same time, switching power converter could be categorized into isolated or non-isolated power converter, and the basic circuit of the converter can be configured to step up (boost), step down (buck), or invert type, even CCM (continuous conduction mode) or DCM (discontinuous conduction mode).
The isolated power converter could be further classified into single ended mode (including forward and flyback converter) and double ended mode (push-pull, half bridge and full bridge converter); the converting technique comprises hard-switched converters and soft-switched converters, and the controlling techniques comprise PFM (Pulse Frequency Modulation) mode control, PWM (Pulse Width Modulation), current mode control, voltage mode control and so on.
Regardless what methods or mode are used, a switching power circuit generally comprises a converter circuit having a power tube, a transformer, an inductance, and at least one rectifying filter output circuit, wherein the quantity of the power tube is subject to the choice of power converter mode, commonly, single ended converter comprises a power tube, the double ended converter comprises a plurality of power tubes. In case of the soft switch is applied, at least one more supplemental power tube is necessary. The inductance here is being used for the simple non-isolated DC/DC converter, while the choice of the chosen converter will simultaneously determine whether the inductance, single-ended or double-ended mode, hard switching or soft switching, to be applied in practice.
Further, the switching power circuit comprises a feedback circuit having a sample circuit, an error amplifier, and occasionally a feedback isolating circuit, wherein the sample circuit is adapted for sampling the current and voltage signal from the output circuit, and sending the sampled current and voltage signal to the error amplifier to obtain a comparative value, afterwards, the error amplifier will output an error signal.
Additionally, the switching power circuit comprises a control circuit including an adjustable pulse circuit and a drive circuit, wherein the adjustable pulse circuit having PFM (pulse frequency modulation) mode, PWM mode and so on. According to the error signal, the adjustable pulse circuit is capable generating a basic pulse, for double-ended mode, there is a scaling-down complementary double pulse circuit, for soft switching multi-pulse circuit, there is a multi pulse circuit. Commonly, basic pulse, double pulse and multi-pulse are supposed to be directed into the driven circuit. It is noted that a bigger error signal will result to a larger duty cycle ratio, as well as a higher peak value of the power tube current and a saturation susceptible transformer.
Finally, the switching power circuit also comprises an supplemental circuit which is selected from a group consisting of initiating circuit, protective circuit, voltage reference circuit, EMC circuit, and alternate rectifying filter circuit, wherein the protective circuit could be further classified into the lower voltage protective circuit, high voltage protective circuit and upper limit current protective circuit. Whenever the switch power supply is initiated or overloaded, the transformer and induction is susceptible to be saturated, and power tube is apt to be loaded with over current. So within the art, the power switching IC employs the upper limit protective circuit for protection, that is to say, when the current reach the upper limit, the power tube will be automatically shut off. Therefore, it is required that the control circuit to be promptly responsible and the power tube be equipped with instantaneously shutting-off function. Otherwise, there exist some sort of hidden risks for the power tube and transformer. For the initiating circuit, there are resistance initiating circuit and switch-off constant current source initiating circuit available within the art.
The single end converter circuit could be categorized into single ended forward converter circuit and single ended flyback converter circuit, wherein the single ended forward converter circuit comprises a magnetically reset circuit which is suitable for a powerful switching power supply.
PFC (Power Factor Correction) could be classified into the single phase PFC and three phases PFC, CCM (Continuous Current Mode) PFC, DCM (Discontinuous Current Mode) PFC, boost PFC, boost/buck PFC converter, and flyback PFC converter. Further, there are constant frequency controlling techniques, constant conduction time controlling technique, and equal area control techniques associated with the DCM mode. And there are peak value current controlling technique, average current controlling technique, lag loop current controlling technique, hard switch and soft switch technique associated with the CCM mode.
Regardless what kinds of converter and switching circuits are being used, a PFC device generally comprises a converter circuit having a power tube, a transformer, an induction, and an output circuit. In case of a soft switch is applied, at least one supplemental power tube and a soft switch circuit are employed. And in case of flyback converting mode is used, a transformer would be necessary.
The PFC device further comprises a feedback circuit having a sample circuit, an error amplifier wherein the sample circuit is adapted for sampling the current signal from the output circuit and then sending the sampled current signal to the error amplifier to generate an error signal.
The PFC further comprises a control circuit including an adjustable pulse circuit and a driven circuit, wherein the error signal is send to the adjustable pulse circuit and the driven circuit is adapted for driving the power tube. It is noted that there is a variety of adjustable pulse circuits available depending which kind of converter circuits and the controlling techniques being used. Commonly, the most used control circuits include constant conduction time control circuit (for example, UC3852, after the power tube is conducted, the induction current will be increased and the conduction time will be determined by the error signal outputted by the error amplifier, after the power tube is shut off, the induction current will be decreased; if the induction current is fallen down to zero, the power tube will be conducted again indicating that the circuit is performing at a transition point between DCM and CCM). Some popular control circuits also include average time control circuit (for example, UC3854 comprising a multiplicator, an current error amplifier, PWM, and an oscillator), flyback converter control circuit, soft switching control circuit, and so on.
Finally, the PFC device also comprises a supplemental circuit which is selected from a group consisting of initiating circuit, protective circuit, voltage reference circuit, EMC circuit, alternate rectifying filter circuit. To prevent the PFC outputting voltage being excess the upper limit, designers within the art have to balance the following factors, such as the outputting capacity of the capacitor, power factors, and total harmonic distortion. In other words, users have to sacrifice some factors to achieve a feedback function. For instance, when the circuit is under a heavy load, the power factor will be reduced and the total harmonic distortion will be accordingly increased. However, sacrifice could solve all troubles, in case of the outputting voltage excesses the design value, or the outputting is converted from a heavy load to a light load suddenly, the control circuit sometimes is unaware or unable to judge whether the outputting voltage being over the upper limit. This is due to some inherent factors of voltage error feedback and input voltage filter waves. As a result, there still exist potential risks in conventional PFC circuits.
A green switch power supply comprises a standby power supply and a main power supply, wherein the standby power supply refers to power-frequency transformer rectifying standby power supply adapted for outputting a voltage range from a couple of watts to a tens of watts. Preferably, the power consumption should be lower under a load-free circumstance. For a green switch power supply adapted for outputting a higher power, a PFC device and EMC circuits are necessary. According to the prior art, the standby power supply and the main power supply are separately designed. At the same time, people have been devoted enormous enthusiasm onto the design of the standby power supply and the single power supply. There is no applications or designs concerning too much about the green switch power supply, i.e. a combined design for reducing the overall costs. For standby power supply, a common approach is to provide a linear regulated power supply, which is not environmentally friendly. A better approach is to provide an independent standby switching power supply, for example, IC switching power supply of TOP series. But this kind of power supply is so expensive.
For the main power supply, there is no special main power IC available in the market. So nowadays, according to the devices and techniques available on the market, the green switch power supply are either so expensive or non-applicable.